1. Field
The present invention relates generally to content distribution systems and, more specifically, to controlling access to selected portions of transmitted digital content.
2. Description
Many different broadcast systems exist which provide analog content to users. For example, radio and television programs are transmitted to consumers via traditional over-the-air broadcast methods, satellites, and cable systems. In most systems, the regulation or censorship of the content is performed by the broadcaster, often in conformance with governmental requirements, and the receiver displays whatever signal is received. In some systems, modification of the content may be performed at the end-user's site. For example, a cable system may transmit a scrambled signal to a receiver, which then decodes the signal if the receiver is authorized to do so. This authorization may occur, for example, if the end-user pays for the programming service or if the end-user enters a passcode to the receiver.
When the content to be broadcast is represented digitally, new opportunities and new problems arise. Digital content may now be broadcast or multicast over broadband channels to many users, perhaps over wide area networks such as the Internet. However, if digital content is transmitted to end-users without adequate security mechanisms in place, piracy of the content may become widespread. Furthermore, if the content is represented and transmitted in digital form, it may be possible to manipulate the content for groups of receivers, or even for individual receivers. However, mechanisms to control the delivery of the content to consumers based on the content itself do not currently exist. What is needed is a way of providing secure conditional access to broadcast digital content based on the content itself, the characteristics of the end-users, and the transmission channels used.